[rygel] build: Bump GSSDP requirement

[Jens Georg <jensgeorg src gnome org>]

commit c49298a9d390231d86f5788639018b9da8ff38ca
Author: Jens Georg <mail jensge org>
Date:   Tue Sep 4 21:50:19 2018 +0200

    build: Bump GSSDP requirement
    
    We need at least 0.14.15 (that's quite old) for
    gssdp_client_guess_user_agent. Bumping was forgotten in commit
    56e4fd19fb

 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/configure.ac b/configure.ac
index ee487ea4..1c2313f4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,7 +37,7 @@ GLIB_REQUIRED=2.40.0
 LIBXML_REQUIRED=2.7
 VALA_REQUIRED=0.24.0
 VALADOC_REQUIRED=0.2
-GSSDP_REQUIRED=0.13.0
+GSSDP_REQUIRED=0.14.15
 GUPNP_REQUIRED=0.20.14
 GUPNP_AV_REQUIRED=0.12.8
 GUPNP_DLNA_REQUIRED=0.9.4